The invention relates to a fuel cut-off apparatus for electronically-controlled fuel injection system of internal combustion engines, which is designed to cut off the fuel supply to an engine during engine deceleration so as to prevent deterioration of the vehicle driving feeling.
Known apparatus of the above type are designed so that the supply of fuel to an engine is cut off immediately in response to a fuel cut-off condition where the opening of the engine throttle valve is smaller than a predetermined value and the engine rpm is higher than a predetermined value. A disadvantage of this type of the known apparatus is that there occurs a great difference between the engine output torque during the injection of fuel and the engine output torque at the instant that the fuel injection is stopped, thus causing shock to the vehicle upon fuel cut off as compared with those having engines which do not cut off the fuel supply. Thus, while this fuel cut-off has the advantages of reduced fuel consumption and improved engine braking effect in addition to a great advantage of preventing a rise in the temperature of a catalyst in the case of vehicles in which an exhaust gas purifying catalyst is installed, there still exists the previously mentioned disadvantage of causing shock to a vehicle. To overcome these deficiencies, it has heretofore been the practice with the known apparatus to accomplish the fuel cut-off within a limited range of engine operating conditions.